Faceplate with land portions having two cavities for receiving shadow mask support members



June 17, 1969 ENGELS ET'AL 3,450,920

FACEPLATE WITH LAND PORTIONS rmvms TWO CAVITIES FOR RECEIVING SHADOW MASK SUPPORT MEMBERS Filed Jan. 12. 1968 Sheet of 5 June 17, 1969 ENGELS ET AL 3,450,920 FACEPLATE WITH LAND PORTIONS HAVING TWO CAVITIES FOR RECEIVING SHADOW MASK SUPPORT MEMBERS Filed Jan. 12, 1968 Sheet 2 of s INVENTORS 55% BY H: t'i lcnMANN AGENT June 17, 1969 G. ENGELS ET AL 3,450,920

FACEPLATE WITH LAND PORTIONS HAVING TWO CAVITIES FOR RECEIVING SHADOW MASK SUPPORT MEMBERS Filed Jan. 12. 1968 Sheet 3 of s INVENTOR6 8. E285 H. WISCHMANN WKMA AGENT P 4 Int. Cl. Hlllj 29/46, 1/96, 19/50 US. Cl. 313-85 6 Claims ABSTRACT OF THE DISCLOSURE A shadow mask is supported by the wall of the window of a color television display tube. This wall has thickened portions for supporting the mask each of which has a recess therein extending parallel to the tube axis for receiving a supporting member for the mask as well as a cavity adjacent to the recess for receiving an additional member for preventing displacement of the mask along the tube axls.

This invention relates to a device for fastening the shadow mask within the upright edge of the display window of a colour television display tube, the wall of the edge being thickened near the areas at which the mask is supported and each thickened area having a groove-shaped recess the opening of which is directed towards the open side of the edge of the display screen.

In the manufacture of a colour television display tube, difficulties are encountered in designing fastening members for holding the shadow mask in position. In fact, the mask is not allowed to shift in the completed tube. Furthermore, the supporting members must be such as to be not damaged when the shadow mask is repeatedly placed in the window and removed therefrom during the manufacture of the phosphor screen, for example, upon exposure of the phosphor layers, while also the original position of the mask is to be retained with very small tolerances. Especial-. ly the fulfilment of these small tolerances has hitherto caused great difiiculty in manufacturing and mounting supports in the upright edge of the display window.

From US. patent specification No. 3,187,404 a support is known where a substantially rectangular display tube has a likewise substantially rectangular shadow mask which is supported by the edge of the display window at three areas. To this end three springs are welded to the supporting frame of the mask, each carrying a pin at its free end. The pins snap into holes formed in the edge of the display window or in the bulb of the display tube. In this way the mask is firmly held in position.

'However, it is dilficult to form the holes accurately and at the correct positions in the edge of the display window, since the location of each hole or the locations of the three holes also determine the position of the mask relative to the display window or to the display screen. In the method known from the said patent specification, elevations are therefore provided within the edge of the display window at the supporting area of the mask. During the moulding of the display window, two grooves of diiferent depths are pressed in each elevation. Metal bodies are secured by means of sintered glass in the grooves located adjacent the open side of the display window. The sintered glass is softened at approximately 400 C. and the display window, which as such is already completed, will therefore have to be heated to this temperature. During this process the edge of the display window is deformed, thereby at nited States Patent the same time changing its position relative to the surface of the display window to which the phosphor layers have to be applied later. This gives rises to a comparatively high loss percentage in the manufacture.

By means of complicated devices a hole for receiving the pin of the mask is drilled into the metal part. During the drilling process, a centering spindle of the drilling device is placed in the second groove above referred to.

German patent specification No. 1,086,813 describes a method in which pins instead of holes are provided in the edge of the display window to fasten the masks. These pins must again be sealed very acurately into the edge at the relevant areas. To permit insertion of the pins the display windows has to be heated to at least 400 C. and further to the softening temperature of the glass at the areas of the pins. In this method, too, the edge itself is deformed and its position changed relative to the surface of the display window, with the same disadvantageous consequences as in the first method described. Since the glass must be softened at the areas of the pins, the pins frequently no longer have the correct positions after cooling of the glass and are, for example, no longer at right angles to the edge. Furthermore difiiculties occur in connection with gas bubbles which are occluded in the glass at the bottom of the pins.

The two methods above described also involve the risk that, for example, due to negligence in placing the mask in the window, either one of the pins falls beside its corresponding hole or the hole of a supporting spring comes to lie beside the associated pin so that the perforated mask drops on the phosphor layer present on the inner side of the display window, with the result that mask has to be cleaned and a new phosphor layer applied to the display window. As a matter of fact, the same thing can happen in taking the mask out of the window.

The present invention makes it possible to arrange supporting members for the shadow mask without heating of the display window being required, thus preventing deformation of the edge of the display window with the consequent disadvantages thereof, while it is neither necessary to drill holes in the edge of the display window with narrow tolerances.

The device according to the invention for suspension of the shadow mask in the manner above described is characterized in that the thickening of the wall includes a recess extending along the tube axis for receiving the pin or spring connected to the shadow mask as well as a cavity formed next to the recess and at right angles thereto for receiving an additional member which prevents displacement of the mask along the axis of the tube.

When using the device according to the invention it can no longer happen that the shadow mask contacts the inner side of the display window on placing the mask into the window or removing it therefrom.

Furthermore, according to the invention, the cavity may be formed as a through hole in the edge of the display window, in which event a metal sleeve with a. connecting strip for the high voltage is placed in the hole in a vacuum-tight manner. Between a flange of the sleeve and the glass of the window edge, there are arranged a connecting strip and a packing ring engaging the glass. The resilient members according to the invention may be such as to engage at one end in the groove and at their other end in the cavity. The springs may also carry two pins which snap into the groove and into the cavity re spectively. Further, the sleeve may comprise two parts, the part situated inside the tube having a flange which electrically makes contact with a resilient clasp which in turn electrically makes contact with inner coatings present on the edge of the display window, on the display window itself and on the cone of the display tube.

In order that the invention may be readily carried into effect it will now be described in detail, by way of example with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 is a plan view on the display window of a substantially rectangular colour television display tube;

FIGURE 2 shows part of the upright edge of the display window with one thickened area in which a groove and a cavity according to the invention have been formed;

FIGURE 3 is a sectional view of the edge of the display window at the area of the cavity in the form of a hole in which a sleeve is placed;

FIGURE 4 is a sectional view of the edge of the display window having a recess according to the invention and a supporting spring carrying a pin, which is secured to the supporting frame of the mask;

FIGURE 5 shows another embodiment in a section similar to that of FIGURE 3;

FIGURE 6 shows yet another embodiment in a section similar to that of FIGURE 3;

FIGURE 7 shows part of a tool (for example a press die) having an exchangeable part for forming the grooves and having a recess for forming the elevation.

FIGURE 1 shows the upright edge 1 surrounding the display window 2, which together form one glass moulding. The edge 1 is provided with thickened parts 3 of glass at three different areas for supporting the shadow mask.

FIGURE 2 shows part of the display window 2 with one thickened part 3. The thickened part has a recess 4 and a cavity 6 which is at right angles thereto. The cavity is ground or milled in the thickened part, after the display window has been moulded and cooled down. If desired, a second cavity 6 may be formed at the other side of the recess 4.

FIGURE 3 is a sectional view of the edge of the display window at the level of the cavity 6. In this embodiment the cavity is a bore in which a metal tube 18 having a flange 21 is fitted in a vacuum-tight manner. The sleeve is surrounded between the flange 21 and the glass of the edge 1, by the annular end of a connecting strip 20 for the high voltage supply and a packing ring 19. The packing ring 19, the sleeve 18 and the bore 6 are formed such that the packing ring 19 is not sucked towards the interior of the tube during evacuation. The sleeve 18 may, of course, also be formed differently and, for example, be cemented in a vacuum-tight manner inside the edge 1. In this case the packing ring may be dispensed with. In FIGURE 3, the sleeve is closed in a vacuum-tight manner by means of a partition 22. The sleeve 18 may alternatively comprise two separate parts with a packing between them. The end of the sleeve which lies inside the tube may be threaded internally or externally so that the sleeve may be fixed in position in a vacuum-tight manner using a vacuum cement and a nut. The nut may have the form of a sleeve which receives the pin secured to the spring which is connected to the shadow mask 11. The manufacture of this construction requires no great accuracy since a shift of the mask has to be prevented only along the axis of the tube, that is at right angles to its own plane, because correct location of the mask is ensured if it is firmly pushed against the base 5 of the recess.

If the sleeve 18 comprises two parts, then the part located inside the tube may have a flange 26 beneath which a resilient clasp 24 is located, which electrically makes contact with the coating on the edge 1 of the display window and also with the coating on the display window 2 itself. By suitable shaping it is furthermore possible to ensure that the clasp 24 electrically makes contact with the coating on the cone 23 sealed to the junction area 25 of the edge 1 of the window. The conventional anode connection on the cone 23 of the tube is thus dispensed with.

The shadow mask 11 can also be connected to the part of the sleeve 18 located inside the tube by means of metal springs.

The two parts of the sleeve 18 may alternatively be connected without the use of a vacuum-tight partition 22, if the one part is provided with a solid, externally threaded end which is screwed into the other, internally threaded part of the sleeve. The sleeves and the screwthreads must have a length suificient for obtaining a mechanically rigid and vacuum-tight connection and securement of the sleeve 18.

FIGURE 4 is a sectional view of the edge 1 of the display window and of the display window 2 and the thickened part 3. The thickened part has a recess 4 with a base 5 which carries a pin 7 secured to a spring 8 so that the spring pushes against the edge of the display window. The spring 8 is secured by means of a rivet or Weld 9 to a frame 10 of the shadow mask. The spring 8 and the pin 7 prevent the shadow mask 11 from shifting in its plane and in the direction at right angles thereto. The mask can thus no longer come in touch with the window 2.

FIGURES 5 and 6 are sectional views of the edge 1 of the display window and of the display window 2 and the thickened part 3, the latter being provided with the cavity 6. Three additional springs 13 and 14 respectively are secured to the frame 10 of the mask 11. In FIGURE 5 the springs 13 are provided with pins or earns 12 which snap into the cavity 6 on placing the mask into the window.

In the embodiment of FIGURE 6, the springs 14 themselves snap into the cavity 6 when the mask is placed in position. This arrangement affords the advantage that the locations of the cavities 6 formed by grinding or milling are not accurately bound to predetermined tolerances with regard to their distance from the edge 1 and from the inner side of the display window 2, since any deviations are neutralised by the springs 13 and 14, respectively, and hence are rather irrelevant. These additional springs also prevent the mask 11 from shifting relative to the diS- play window in the direction along the tube axis. Since the mask furthermore pushes the pin 7 against the base 5 of the recess 4, the mask is locked against displacement in all directions and cannot fall out of the edge of the display window.

The springs 8, 13, 14 may be so formed that one end snaps into the recess 4 and the other snaps into the cavity 6, the spring itself being secured to the frame 10 of the mask. A similar result can be obtained by providing each of the springs 8 and 13 with two pins 7 and 12 respectively.

FIGURE 7 shows a portion of a press die 15 for forming the display window, that is to say the edge 1 and the display window 2 itself. The surface of the die has a cavity of suitable shape which serves to form the thickened part 3. A mandrel 16 for pressing the recess 4 in the thickened part 3 is secured in the base of the cavity. The mandrel may be detachably secured and hence be exchanged if the mandrel has worn out to a greater extent than the remaining parts of the die.

What is claimed is:

1. Means for supporting a shadow mask in a color television display tube having a window with a wall having thickened portions for supporting the mask, each of said thickened wall portions having a groove-shaped recess extending parallel to the tube axis and opening out into the interior of the tube, a support member secured to said mask extending into each of the recesses, each of said wall portions further having a cavity therein adjacent said recess, and an additional support member secured to said mask extending into each of the cavities for preventing displacement of the mask along the tube axis.

2. A device as claimed in claim 1, wherein the cavity is formed in the wall of the display window as a bore and a metal sleeve with a connecting tongue is fitted into said bore in a vacuum-tight manner.

3. A device as claimed in claim 2, wherein said sleeve has a flange and a connecting strip and a packing ring are present between the flange of the sleeve and the wall.

5 6 4. A device as claimed in claim 1 wherein the support References Cit d members include springs one end of each of which snaps into the recess and the other snaps into the cavity. UNITED STATES PATENTS 5. A device as claimed in claim 4 wherein each spring 9 9 9/ 1959 Wollghtel' et has two pins which snap into the recess and cavity re 9 9 3/ 1960 Hoaglandspectively. 5 3,358,170 12/1967 Fiore.

6. A device as claimed in claim 2 wherein the sleeve comprises two parts of which one is located inside the ROBERT SEGAL: Primary Examinerdisplay tube and has a flange which electrically contact with a resilient clasp making electrical contact with inner coatings present on the wall of the display window, on 10 313-286, 288 the display window and on the cone sealed to the wall of the display window. 

